Loading

Module 1: Extrusion Based AM and Metal Powder Manufacturing

Notes d'étude
Study Reminders
Support
Text Version

Metal Powder Manufacturing and Characterization

Set your study reminders

We will email you at these times to remind you to study.
  • Monday

    -

    7am

    +

    Tuesday

    -

    7am

    +

    Wednesday

    -

    7am

    +

    Thursday

    -

    7am

    +

    Friday

    -

    7am

    +

    Saturday

    -

    7am

    +

    Sunday

    -

    7am

    +

Metal Powder Manufacturing and Characterisation
Good day. This is Manoj Kabre, Vice President Sales and Marketing from INDO-MIM. Weare the world’s largest company engaged into a very unique and emerging technology calledmetal injection molding and in addition to that over the last few years, we have also startedmetal powder production and today I am going to discuss with you more related to the metalpowders for additive manufacturing which is something which is catching up a lot.(Refer Slide Time: 00:59)
So, friends, in the content we are going to talk about the introduction, the metal powderproduction techniques, the facility for metal powder production that is the one which is atINDO-MIM. We are one of the only companies having this kind of unique power productionfacility. We also talk about INDO-MIM metal powders that is what kind of metal powdersare being used at INDO-MIM. So we talk about that.
We talk about qualification and controls at INDO-MIM for metal powders and we talk aboutmetal powders for Mega drivers like what are the main areas where these metal powders foradditive manufacturing have been really catching up or what is scenario in the industrialmarket look like and of course we talk about our core technology metal injection moldingbefore we close for the day. So, I hope this kind of content is aligned to your expectations.
So, let me commence the introduction.(Refer Slide Time: 02:09)
INDO-MIM is a metal injection molding company and metal injection molding is one of thebranches of powder metallurgy as few of you might know. We have one of the largestfacilities in the world to make MIM components. We have a global market share of roughlyabout 14%. Actually, this entire market of metal injection molding is very scattered. So it hasa very long tail if I may say so and we are of course the world number 1 and the worldnumber 2 is roughly about one third of our size and then of course you have a lot of othercompanies.
There are roughly about 100 companies in China, there are about 50 odd companies in Japan,similar number in Europe and so on. INDO-MIM has 3 manufacturing location in India, 2 formetal injection molding and 1 for investment casting. We started about 3 years back alsogreen field metal injection molding plant in USA. We as I mentioned earlier are the firstIndian company to install a commercial scale hot gas automizer. This was done about 4 yearsback in 2006 in Bangalore at our Doddaballapur facility.(Refer Slide Time: 03:40)
Let us focus some time on metal powder production techniques because I am sure all of youmight be curious as to what kind of metal powder production techniques are used, what aretheir merits? What are their demerits? Why are there multiple metal powder productiontechniques? So, I mean one thing which all of you probably might be able to visualize orimagine is a mechanical processing or you also call it milling or grinding of powders
Now mechanical processing provides irregular shape and this is something which is usedwhere quality is not of prime importance. Simple example that I could site would be gascutting or welding application. So, this is something which us used for mechanicalapplication and aluminum powder which is subjected to mechanical milling is also used intracking application so that is another application for that.
So, predominantly mechanical processing is something which is used where quality is not ofparamount importance and where scale is of importance. So, mainly I would say it is mainlyfor general applications. The second technique which is pretty popular is called pyrolysis or Iwould say carbonyl decomposition and electro deposition. This is used mainly for powdersize less than 10 microns.
So, food industries, iron vitamins industrial application these are some of the application andthen you have basically molybdenum which has a melting point of about 2700 degreecentigrade, so that is some powder where high melting point is one of the prerequisite forgetting into carbonyl or electro deposition or reduction technique. Tungsten might be anotherexample which also has high melting point.
And then the carbonyl route is something which is used for production of sized powders andthen the other technique that you do very popular is called atomization, which is mainly forbulk or cost-effective production and within atomization there are 2 types. One is wateratomization and another one is gas atomization. So, water atomization is something which ispretty popular and again simple example could be iron powder.
Iron powder which is usually made by water atomization, where you get irregular shape inwater atomization. You have to do additional operation like dewatering, like drying which ofcourse consumes some time, but ultimately you end up spending a lot less amount ofexpenditure as compared to gas atomization. Water atomization is a technique that produces abit of irregular shape.
It again can be used for areas where oxygen content or nitrogen content is not very important.So, what is happening here is that there is a pick up of oxygen and nitrogen content fromwater or even hydrogen content from water and that something which remains in the powderwhen you use a water atomization technique. So, these basically I can call these as impurities,presence of oxygen and nitrogen.
The application of water atomization typically iron are areas where you may not want theseimpurities to be below a threshold level of a few ppm. The technique which INDO-MIM hasbeen focusing on is called gas atomization and gas atomization is predominantly a techniquewhere you would have these ppm of all hydrogen, oxygen, nitrogen to be below somethinglike 100 ppm.
I mean there are techniques available where you can even control them below 100 ppm andthere are various applications starting from aerospace or starting from medical devices oreven oil and gas sectors where these kinds of gas atomization techniques or productionmethodology is used because you have a very clear focus on controlling the ppm levels ofthese impurities, because these are going to affect the end product quality in a direct way.
At INDO-MIM we have been focusing on utilizing this gas atomization process as well asfurther perfecting it such that we are able to give the product of quality as required by thesedemanding industries.
(Refer Slide Time: 08:49)
Delvin Littlebird further on gas atomization process which is widely adopted. The gasatomization process can be implemented or the production can be done using two specificmethods, one is called vacuum induction melting plus inert gas and the electrode or plasmamelting as it is also called plus inert gas atmosphere. So basically, we have inert gas as animportant element in both these processes.
But the specific discrimination as you can see on this slide between these two processes isthat one is using a crucible whereas second is not using a crucible. Vacuum induction meltingis something which is one of the most popular method that is used for producing most of thealloy steels, stainless steels, nickel and cobalt super alloys. It is basically a process wherebyyou have a crucible into which this particular molten metal is poured.
The crucible is mainly having some amount of silica or aluminium oxide, which probablywould get mixed up with molten metal thereby because of it there is some gas which getseroded and mixed and these are some of the inclusions which may be present inside themolten metal while it is getting atomized and it can certainly achieve aero-grade purity levelbut not to there, I mean I would say about 70% of the application of aerospace would beutilizing this kind of vacuum induction melted gas atomization process.
Whereas some of the demanding application probably 25 to 30% might not be able to use theproduct out of vacuum induction melting and also it is not suitable for reactive metals. So, insummary, vacuum induction melting has a crucible, it enables some of the impurities or
material of the crucible to be mixed along with the molten metals while the melted metal isbeing poured and it is used for about 70% of the aerospace application.
Coming to electrode or plasma melting, again here as I said it has inert gas and it is termed asa ceramic free melting process. It is used mainly for refractive metals. The simplest thinghere is that the inclusions which normally come because of the presence of crucible are goingto be absent here and that clearly indicate that you would not have impurities and hence thepopulation of spherical powder is going to be more. Certainly, this is an expensive route.
But then if you have any conventional alloys also to be produced here because of this puritycontent or because of this higher population of spherical powders, it is definitely preferred.The highlight here is that the electrode that itself acts as a crucible here. So, there is no formalceramic crucible that is used here since it is a ceramic free melting process, but the electrodeitself acts as a crucible and the melting process takes place using this plasma.(Refer Slide Time: 12:18)
So let us come to the hot gas atomization process flow as this slide briefly explains you theprocess flow that is being implemented at INDO-MIM. We have basically the 7-step processwhich is given in this flow chart. The first as you would obviously understand or appreciate isincoming inspection. The raw material is coming into the plant. There is a formal way ofincoming inspection which is done. The second process is melting.
Melting is where the molten metal is poured and this we have something called a tundishprocess, whereby there is a large vessel in which there is small orifice at the end. It will be
poured from the crucible into this tundish and this allows the flowability of the molten metalthrough this small orifice about 6 mm or so before it goes for the atomization process. Nowfriends what happens in atomization process is that there is a gas which flows at a velocity ofsomething like 1 one or 1.5 mac, 300 meters per second or something.
And under that high pressure when this 6 mm orifice is leading some hot molten metal intothe large vessel that is where this atomization takes place. The facilitation of atomization istaken place through the high velocity of the inert gas and once the atomization is done, whatyou have as a result of it is probably particles less than 5 microns going up to about 150-200microns. So, it is a very wide array of particles that would come as a result of atomization.
So, necessarily what we need to do is we need to screen them. The next process is screening.What do you mean by screening? Screening is basically classification of these powders intodifferent size levels. We have for instance less than 20 microns which is used for metalinjection molding, 20 to 50 microns is used for some of these additive manufacturingprocesses. The most popular band for additive manufacturing is 50 to 150 microns andbeyond 150 microns is used for other processes.
So the major powder which is used is between this 0 to 150 microns and that is somethingwhich is done through this screening process. Subsequent to that we have blending process,again where our team has done some wonderful work of establishing fine processes thatenables us to have very good blending, which subsequently goes to the quality check. Soquality assurance is the area where we do this quality check.
We have various in process inspection stages while we go through these processes, butquality check at the end of the completion of blending is something which is done before wepack these products into pre-determined boxes or predetermined packaging sizes.(Refer Slide Time: 15:29)
So here is an image of the large-scale hot gas atomizer that is available at INDO-MIM. Wehave a melt capacity of about 600 tons per annum and this is vacuum melting or hot inertnitrogen gas atomization process. I will talk about ASB features, anti-satellite features, thatthat our team has wonderfully worked along with the supplier to have this kind of feature thatis mainly helping us to have very good powder sphericity.
On additive manufacturing, we are focusing a lot, currently we have about 100 tons ofcapacity dedicated for additive manufacturing out of these 600 tons that we have and we areplanning to enhance this capacity to roughly about 300 tons per annum by the year 2022.Currently we are able to handle ferrous alloy, nickel and cobalt super alloy powders and wecertainly plan to get into new and new varieties of powder based on the demands from ouradditive manufacturing folks across the country as well as internationally.
I am very pleased to say at this stage that majority of additive manufacturing shops in thecountry today have switched over to INDO-MIM powders and they are pretty happy andpleased with the performance of our teams, both the technical as well as the commercialteam. I mean, just to say that the pricing wise we are competitive and we are also able tosupport most of these additive manufacturing jobs.
With respect to specific powders that they need, with respect to R& D efforts that they need.Many times they need specific controls on flow rate at their end. So, to enhance the printquality we have been able to do a good work with respect to providing them right technicalsupport in terms of a powder manufacturer.
(Refer Slide Time: 17:24)
So, expanding further when we talk about the powder requirements, as you all know there aremultiple additive manufacturing processes starting from DMLS, EBM, DED, majority ofthem and then of course we make powders for metal injection molding as well as binderjetting and press and sinter. Press and sinter is the routine powder metallurgy age old process.So, in the second row you can see the particle size distribution in microns that is given for allthese different kinds of processes.
For instance, DMLS, direct metal laser sintering uses 15 to 50 microns. EBM, electron beamuses 50 to 150 microns, same is the range of particle size distribution used for DED. Metalinjection molding as I said earlier uses less than 20 microns, so roughly about 4 to 22microns. Binder jetting is another very interesting process that INDO-MIM has gotten to inthe last 18 months or so, where again the powder size that is used is about 5 to 25 microns orgoing up to 40 microns in critical cases, beyond 40 microns. That is from 45 to 180 micronsis something which is used for press and sinter.
The third row as you can see is about the particle shape. Majority of additive manufacturingrequires a spherical shape that is one of the important requirements for having a betterprinting quality, whereas metal injection molding uses spherical or irregular shape. You needto have a combination of these shapes. That is something which enables you to have a betterpacking in metal injection molding. Binder jetting also requires spherical shape and of coursein coming to press and sinter you have combination of spherical and irregular shapes.
Size distribution width is something which I would like to draw attention from all of you thatis the fourth row, which clearly highlights what kind of size distribution width is somethingwhich is used for various additive manufacturing processes as well as metal injectionmolding, binder jetting and press and sinter process. So, you would see that typically additivemanufacturing oscillates between about 1.34 to 1.38 as far as the size distribution width isconcerned, whereas when we go to metal injection molding, it is going to be higher one pointseven five 1.75.
Binder jetting again going higher to 1.83 and of course the press and sinter uses about 2.02 asthe processing or the size of distribution width as 2.02. I would draw your attention to thissize distribution width because this is something which additive manufacturing focuses on.So typically for additive manufacturing, we need a little, I would say narrow distribution thatdirectly affects the print quality. You can see in this chart that 1.34 to 1.38 is the sizeinstitution width that has been used for additive manufacturing. Again, to highlight littlefurther in case of metal injection molding, you have a higher size distribution width.
Again, there is a reason for it because by having this you are able to have a better packing interms of holding process and other things and binder jetting if you would know is also verysimilar to metal injection molding, just that molding element of metal injection molding getsreplaced with printing in case of binder jetting. Whereas the debinding and sintering definingprocesses that I will explain a little further when I go to metal injection molding is alsopresent in binder jetting.(Refer Slide Time: 21:30)
Challenges in the AM industry, I think all of you probably are aware that additivemanufacturing is certainly going through a lot of difficult times. I mean there was a definitelya hype about additive manufacturing catching up really quick, but then there are mainly these4 challenges, which are mainly affecting most of the job shops or 3D printing shops. Highcost, lack of experience, feedstock, and complex design.
So, these are the main 4 things which are going to be affecting the growth of additivemanufacturing industry. When we say high cost, it is basically because of low productivity asyou would know or probably imagine. The other reason also for high cost is scrap from failedprints. So basically, yield that is coming out of additive manufacturing process is not verygood, going to be failed prints and the second important thing is the setup time.
These are the 3 main elements which are contributing to high cost in the additivemanufacturing process. I mean, it is a relatively new technology. I am sure all of you knowthat additive manufacturing is not very old in terms of technology, although there has been alot of research going on, especially in the West and the second important area why additivemanufacturing is struggling or in the factor of lack of experience is the challenging part.
I mean, I am sure you know that aerospace is something or oil and gases are industries whichare trying to utilize or I would say exploit the additive manufacturing technology to a verylarge extent, and hence most of the designers are being allowed to make as much challengingpart design as possible and most of the additive manufacturing jobs are having difficulty inproducing these part designs. So, these challenging part designs are one of the reasons that iscausing the additive manufacturing jobs not to be quite successful that is of course acting as achallenge.
Feed stock, this is another area which is an important challenge, but mainly being focused byINDO-MIM our company. There are limited ranges as you would know in terms offeedstock. The controls in feedstock properties is something which is critical, mainly withrespect to achieving reproducibility. I would come a little further on talking more about howINDO-MIM has really focused more on getting this feedstock thing done and we have beenable to support our own captive requirement as well as most of the customers. The fourth andfinal challenge named is of complex design.
So basically, we have difficulty in finishing the parts. Most of you would know that additivemanufacturing does not give a very good surface finish. So, we need to necessarily have apost additive manufacturing finishing process. The support structure removal is an elementwhich has to be necessarily done irrespective of what kind of additive manufacturing processwe do and inspection is an important element that takes up a lot of time. So, these are the 3parameters under the complex design category that is acting as a challenge to the AMindustry.(Refer Slide Time: 25:03)
So having briefly discussed about these points, let me now talk about INDO-MIM metalpowders as to what kind of metal powders INDO-MIM is specifically focusing on, what arethe powders that we have included in our basket. We have basically four categories or fourbasic heads under which we are manufacturing powders and supplying to the additive
manufacturing industry. One is stainless steel where we have almost all the major fast-moving stainless-steel items under this particular group SS 316L, 17-4 PH, 15-5 PH, SS 304,
SS 321, SS 310 and martensitic stainless-steel SS 420.
These are the main fast moving stainless steel that we are producing regularly and we havestocks of these orders at all points of time. When we come to the alloy steel, we have beenmaking MA 300, H13, tool steels like M2 and D2. We make bearing steel 52100 and we alsomake 4240. So, these are the alloy steels. Again, based on the research that our sales andmarketing team has done with respect to what kind of powders are required in the market,these kinds of items have been used.
Nickel alloys is something which is one of the fast-moving product categories at INDO-MIM,mainly used by aerospace applications as well as some of the oil and gas applications. Inconel718, Inconel 713C, Inconel 625 and one of the very popular method popular powder that wemade is called NIMONIC 90. These are the four categories of nickel alloys that we aremaking. Coming to Cobalt alloys, T400, T800 these are the commercial names that we aredoing is high cobalt powders mainly used for high temperature applications.
We are using F75 also as one of the powders high cobalt chromium which is used for militarygrade. We do produce Stellite 6 and of course we are producing Haynes 25 also. So, these arethe 4 broad categories of powders that we are making and I also narrated all the specificnames of the powders. This is something which will help you to remember the variety ofthese powders.(Refer Slide Time: 27:16)
But of course, producing powders is just not enough, what is important is qualification andcontrols. So, let me take some time and explain to you what kind of qualifications andcontrols are available at INDO-MIM. In brief, these are the 4 primary characteristics as wellas the 4 secondary characteristics that are being controlled at INDO-MIM. What you wouldsee is that the primary characteristics are particle sizes and distribution, particle shape,chemical composition, and particle density.
These are the 4 primary characteristics that INDO-MIM focuses on, which in turn helps is tocontrol the apparent or bulk density, flow rate, tap density as well as compressibility andgreen strength. So as you would appreciate that the quality control is something which is
important for us to get the powder to the additive manufacturing folks whereby they are ableto utilize them in a better way and the properties which are listed down here these aresomething which have the minimum for these additive manufacturing folks to be able to usethis powder and have lower field print rates.
Now, what we are doing at INDO-MIM is that we are fine tuning our process design. We arecontinuously iterating the process and having better controls so as to have all these particleshapes and distribution, particle density that enables us to have mainly better tap density andflow rate. Flow rate is something which is an important secondary characteristic that directlyaffects the printer and the inhouse process capability measures that we have adopted that issomething which is helping us bring a better control in terms of powder consistency.
I have also included in the presentation some of the control charts which will have you proofof the pudding is an eating kind of concept whereby you are able to see what kind of controlsare actually being given out at INDO-MIM batch after batch. The particle size distributionand morphology indirectly control the apparent density and flow rate as I was mentioningearlier. So just to kind of give you a kind of thumb rule, so if there is a good powder whatwould happen is you pick up 50 grams of powder, pass it through an orifice of say 1 inch, itshould take less than 20 seconds to flow.
So this is one of the easiest or benchmark kind of a method by which you are able tounderstand if the flow rate of the powder is good and if it is going to be helpful for theprinting platform.(Refer Slide Time: 30:18)
I was mentioning about these controls. So here are some of the particle size distributioncontrol charts. In the upper chart, you see D10 in microns and what you are seeing there is theblue one, which is the lower specification limit, the orange one is the upper specification limitand at the center is the D10 control on particle size distribution, starting from batch number 1to batch number 17. So, what is controlled at INDO-MIM in terms of the process parametersis what is reflecting here in terms of results.
So, well within the upper and lower specification limit. Same thing you can see in the D50fraction trend. Again, the blue is the lower specification limit, orange is the upperspecification limit and the D50 line as you can see or trend as you can see from batch 1 tobatch 17. We have just taken some example here that shows you that the output is very muchin control within the upper and the lower limit.(Refer Slide Time: 31:26)
Here, you have the controls on PSD for D90 fraction trend. So again, you can see between thelower and upper specification limit, D90 is pretty consistent, pretty low in terms of thevariation and the last one is D99 where of course there is only upper specification limit andagain D99 is pretty much controlled.(Refer Slide Time: 31:54)
When we talk about powder’s particle size distribution trends, it is important to have thesechecked, the powder properties to be checked. So, these are some of the popular methods thatare being used by the industry starting from dynamic image analysis, static image analysis,sieve analysis, diffraction and dynamic light scattering. So you can see on the right-sideagainst each of these methods we also given the range for this particle size distribution. Forinstance, for dynamic image analysis, it is 0.8 microns to 135 microns.
For laser diffraction it is about 10 nanometers to 5 mm. I mean we at INDO-MIM of courseuse laser diffraction. On the right-side you can see the Mastersizer 3000-Malvern that is theinstrument that we use. We control from 1 micron, starting from 1 micron upwards using thislaser diffraction method, but just out of academic perspective, I thought we should includethese different methodologies as well as the range that they can qualify or that we can check.(Refer Slide Time: 33:27)
So having talked about the particle size distribution or methodologies to check them powderproperties and all, I think it is time for us to switch over the gears to particle shape. This isanother important parameter that needs to be controlled when we come to additivemanufacturing and what does particle shape play in terms of role? So, it has a very significantrole in powder methodology whether it is additive manufacturing or metal injection moldingand shape is basically decided based on the application.
If you remember early on I just mentioned briefly that additive manufacturing needs sphericalshape for having a better printing quality, whereas metal injection molding wherein you mixthe powders along with the binders and you need something called green strength, there youneed a very good combination of irregular shape as well as the spherical shape. So, theparticle shape is going to be one of the main parameters I would say, which is going to affectthe process and in case of metal injection molding, the way it would be optimized is that itwould enable dense packing to be done by having this kind of combination.(Refer Slide Time: 34:29)